This is a piece of javascript code I use to detect whether my library is inside an iframe.
1 out of 100% of requests report that my library is inside an iframe which I think is not possible.

Is there a possibility that this code to fail [report true on false or vice versa]?

From access log [I log every such iframe requests]

I found that it happens in all modern browsers [ie 6-9, chrome, ff, safari] from user agent string.

I couldn't make any sense out of referrer because they are same as my publisher site.

In some cases I found for same referrer, same url requested & same client ip my library had been once inside an iframe & not in other. This made me doubt the above code.

Will there be any difference while window or document is being loaded in the properties [self, location, top, parent] I use to check? Because my script loads and executes synchronously mostly before the document is ready or window is completely loaded and that does the iniframe test to proceed further.

3 Answers
3

You know most modern browsers allow you to "View Frame" right? As in, view the frame content without the parent. That's an entirely plausable answer for 3. (I do it all the time).

A plausible cause of 1 and 2 is that self is not really defined in javascript therefore may not always be equal to window. You should therefore be checking window or better yet window.self not self like Özgür suggests.

If all you're trying to do is detect when your code is in a frame of any kind, all you need is this:

if (window.top !== window) {
// you are embedded in a frame
}

or to set your variable inFrame like this:

inFrame = (window.top !== window);

or in function form:

function isInFrame() {
return (window.top !== window);
}

As long as you aren't accessing properties on the window.top object, you shouldn't need exception handlers to protect from cross domain parents. In a cross-origin situation, you can access window.top, but you cannot access properties such as window.top.location.href.

As for your other questions:

Is there a possibility that this code to fail [report true on false or vice versa]?

The first part of your code looks OK though the exception handler is not required. The second part of your code will throw an exception every time in modern browsers when the window and parent frame are different origins.

Will there be any difference while window or document is being loaded
in the properties [self, location, top, parent] I use to check?
Because my script loads and executes synchronously mostly before the
document is ready or window is completely loaded and that does the
iniframe test to proceed further.

At the point your window is loading, it is safe to make this check. Both window and window.top will be valid at that point even if neither has completed loading yet. So, there should not be any issues with inFrame detection that require you to wait for anything to complete loading.